Connect the amplifiers to each other on the scheme of the serial connection. So, the output negative connector of the first amplifier, then connect the negative terminal of the second amplifier. Connect the positive output terminal of the first amplifier with the positive output terminal of the second. With such simple operations, you will be able to provide a consistent experience from two of the amplifiers and increase the power of the audio system as a whole. However, you should pay attention to the indications of the output current so that its value does not exceed the permissible limits.
Before setting up the amplifier make sure that the resulting output terminal coincides with the entrance speakers. In addition, take care of connecting the amplifiers by connecting the wires of reasonable length. It is best to choose a wire gauge as high as possible. The smaller the gauge the bigger the wire diameter, but it is not always convenient. Usually, speakers take the 14th assortment, but you can choose less, but with sufficient length of wire and in the presence of a speaker system good power.
Test evaluation of amplifiers. It is necessary to determine the quality of the work performed and eliminate possible defects and interference. Pay attention not only on sound quality and functionality (though it is the main indicators of successful work), but also on the external aesthetic appearance.
When connected to amplifierm subwoofer, you have to remember about active and passive subwoofers. An active sub has a built-in amplifier, which allows to remove the burden on low frequency amplifiers. Passive does not have its own amplifier, so the connection must be made consistently with the speakers. Diagram for connection shall be attached to any user manual.